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Innate Immunity

Cell Biology

  1. Osamu Takeuchi1,2,
  2. Shizuo Akira1,2

Published Online: 15 SEP 2006

DOI: 10.1002/3527600906.mcb.200400142

Reviews in Cell Biology and Molecular Medicine

Reviews in Cell Biology and Molecular Medicine

How to Cite

Takeuchi, O. and Akira, S. 2006. Innate Immunity. Reviews in Cell Biology and Molecular Medicine. .

Author Information

  1. 1

    Osaka University, Osaka, Japan

  2. 2

    ERATO, Japan Science and Technology Agency, Osaka, Japan

Publication History

  1. Published Online: 15 SEP 2006


The innate immune system utilizes a limited number of germline-encoded pattern-recognition receptors to sense invading pathogens, and is evolutionally conserved from Drosophila to vertebrates. The mammalian innate immune system is subdivided into three different mechanisms. The first mechanism is the lectin-complement pathway, which recognizes invading microorganisms using plasma proteins such as lectin. The second mechanism is the Toll-like receptor (TLR) pathway, which detects pathogen-specific molecular patterns (PAMPs) shared by broad classes of microorganisms via TLRs on the membranes of innate immune cells. Each TLR activates a distinct signaling pathway by recruiting different TIR-domain containing adaptor molecules. The pathways lead to activation of the transcription factors NF-κB, AP-1, and interferon regulatory factor 3 (IRF3), followed by rapid induction of proinflammatory cytokines and type I interferons (IFNs). The third mechanism is mediated by cytoplasmic pattern-recognition receptors that detect microorganisms in the cytosol, and also leads to the production of cytokines and IFNs. These innate responses also instruct acquired immunity by expressing costimulatory molecules and presenting antigens for recognition by lymphocytes.


  • Innate Immunity;
  • PAMPs;
  • TLRs;
  • TIR Domain;
  • NOD-LRR Family